Optical relay systems may typically generate an image of a particular optical plane of an optical system at another point in the optical system. For example, an optical microscope may generate an image of a sample at an intermediate plane within the microscope and include an optical relay to relay the image of the sample to a detector. As another example, an angular scatterometry system may provide a pupil plane containing angularly resolved light from a sample and an optical relay to relay the pupil plane to a detector.
Typical optical relay systems utilizing on-axis optical elements may suffer from artifacts that may degrade the relayed image. For example, on-axis refractive optical elements may generate ghost images associated with reflections from optical surfaces. Further, refractive surfaces may absorb select wavelengths of illumination (e.g. ultraviolet wavelengths) and/or induce chromatic aberration. By way of another example, on-axis reflective optical elements may typically require holes or obscurations to allow for the propagation of light that may induce artifacts in the relayed image. By way of an additional example, off-axis reflective optical elements may introduce aberrations (e.g. astigmatism, coma, or the like induced by spherical optical elements) or require relatively expensive aspherical optical elements to provide aberration-corrected relay planes.
Therefore, it would be desirable to provide a system and method for curing defects such as those of the identified above.